The present invention relates to testing of concrete in fabricated structures or components thereof, and particularly nondestructive testing thereof.
It is frequently desirable to be able to test concrete structures, or sections of such structures, in order to determine whether they have the requisite strength and structural integrity. Heretofore, testing of concrete strength has involved destructive procedures which can not be applied directly to structures that are to continue in use.
In addition, it is known that concrete will experience deterioration over the course of time, which deterioration can be accelerated if the initial concrete composition deviated from that desired, and/or if the concrete was poured under less than optimum atmospheric conditions, and/or if the concrete was subjected to extreme weather fluctuations and/or earth tremors, etc. In the case of concrete structure which are reinforced by steel bars or rods, the reinforcing bars can experience substantial deterioration, particularly if the concrete develops cracks which allow water and air to come in contact with the bars. Presently, there is no convenient procedure for monitoring the physical state of a concrete structure periodically in a nondestructive manner.
U.S. Pat. No. 3,700,850 (Lumley et al) describes removal of material from a workpiece by laser pulse impacts. Each laser impact generates an acoustic shock wave which is propagated through the workpiece. The time of passage of a shock wave from the point of radiation impact to a sensor is indicative of the amount of material removed. When the time of passage has a predetermined value, it is concluded that a predetermined amount of material has been removed from the workpiece. This patent does not identify suitable workpiece materials, but those skilled in the art would understand that machining, the term employed in the patent, is generally performed on metal or plastic workpieces.